FIG. 1 depicts a cross-sectional view of the image forming apparatus 100 know in the art. The image forming apparatus 100 may be color and/or black-and-white copiers, color and/or black-and-white printers, and/or so-called “all-in-one devices” that incorporate two or more functions such as scanning, copying, printing, and faxing capabilities in one device.
Referring to FIG. 1, a photosensitive drum 1 on which a latent image may be formed may be rotated in the direction of arrow A, and may be uniformly charged by a charging apparatus 2 for charging the photosensitive drum 1, and an electrostatic latent image is formed on the surface thereof by a laser beam 3 from an exposing unit for writing the electrostatic latent image on the photosensitive drum 1. This electrostatic latent image may be developed and visualized as a toner image by a developing assembly 4 disposed in proximity to the photosensitive drum 1. The developing assembly 4 is further described in more detail below with reference to FIG. 2.
As known in the art, the visualized toner image on the photosensitive drum 1 may be transferred to paper 13 which is a recording medium by a transferring roller 9. Any residual toner left on the photosensitive drum 1 may be scraped off by a cleaning blade 10 and contained in a waste toner containing container 11. On the other hand, the paper 13 to which the toner image has been transferred is subjected to the fixing process by a fixing apparatus 12 and is discharged out of the apparatus and thus completing the printing operation.
The developing assembly 4 will be further described next with reference to FIG. 2. In FIG. 2, the reference numeral 14 designates a developing container as the developer container containing therein a magnetic/non-magnetic toner/developer 8.
The developing assembly 4 may be provided with a developing roller 5 as the developer carrying member located in an opening portion of the developing container 14 and disposed in opposed relationship with the photosensitive drum 1, and is adapted to develop and visualize the electrostatic latent image on the photosensitive drum 1. The developing roller 5 may be in contact with the photosensitive drum 1.
The specific developing operation is such that the magnetic/non-magnetic toner/developer 8 in the developing container 14 is sent toward a roller 6 with the rotation of an agitating member 16 in the direction of arrow C. In one exemplary embodiment, the roller 6 may be an elastic roller. In another exemplary embodiment, the roller 6 may referred to as a toner adder roller. Next, by the elastic roller 6 being rotated in the direction of arrow D, the toner/developer 8 is carried to the vicinity of the developing roller 5, and in the contact portion between the developing roller 5 and the elastic roller 6, the developer 8 carried on the elastic roller 6 frictionally contacts with the developing roller 5 and is thereby subjected to frictional charging, and adheres onto the developing roller 5. Thereafter, with the rotation of the developing roller 5 in the direction of arrow B, the toner 8 is sent under the pressure contact of a blade 7, and is formed into a thin layer on the developing roller 5. In one exemplary embodiment, the blade 7 may be an elastic blade. In another exemplary embodiment, the blade 7 may referred to as a regulating member or a doctor blade. The layer of the magnetic/non-magnetic toner 8 formed as the thin layer on the developing roller 5 is uniformly carried to a developing portion which is a portion opposed to the photosensitive drum 1. In this developing portion, the layer of the toner 8 formed as the thin layer on the developing roller 5 develops the electrostatic latent image on the photosensitive drum 1 as a toner image by a DC voltage applied to the developing roller 5.
Any un-developed toner 8 not consumed in the developing portion is collected from the lower portion of the developing roller 5 with the rotation of the developing roller 5. A seal member 17 comprising a flexible sheet (sealing blade) is provided in this collecting portion and permits the passage of the undeveloped toner into the developing container 14 and also prevents the magnetic/non-magnetic toner 8 in the developing container 14 from leaking from the lower portion of the developing roller 5. The seal member 17 is shown in FIG. 1. This collected undeveloped toner on the developing roller 5 is scraped off from the surface of the developing roller 5 in the contact portion between the elastic roller 6 and the developing roller 5 and at the same time, fresh toner is supplied onto the developing roller 5 by the rotation of the elastic roller 6, and the aforedescribed action is repeated.
In order to prevent the leakage of the toner 8 from the vicinity of the end portions of the developing roller 5 to the outside, i.e., the so-called toner leakage, end portion seal members 19 as the seal members are discretely provided near the end portions of the developing roller 5. One of the end portion seal members 19 is shown with doted lines in FIG. 1 and solid lines in FIG. 2.
FIG. 3 shows the front structure of the developing assembly 4 shown in FIGS. 1-2. FIG. 3 is a view of the developing assembly 4 as it is seen in the direction from the photosensitive drum 1. For ease of reference, the developing roller 5 is not shown in FIG. 3. FIG. 4 shows the front structure of the developing assembly 4 with the developing roller 5. The side surface portions of the end portion seal members 19 are disposed so as to contact with the opposite end surface portions of the elastic blade 7 and the surface of the developing roller 5 to thereby prevent the leakage of the toner 8 from the opposite end portions of the elastic blade 7 and the developing roller 5. As the developing roller 5 rotates in the direction of arrow B, the surface of the developing roller 5 is in frictional contact with the end portion seal members 19 to prevent the leakage of the toner 8. As known in the art, the end portion seal members 19 may comprise a fibrous material such as woolen felt or PTFE pile, or a foamed material such as polyurethane foam, or sponge rubber, or molded silicone.
Throughout the operational life of the developing assembly 4, the developing roller 5 rotates thousands of times which results in formation of gaps between the developing roller 5 and the end portion seal members 19 and leakage of the toner 8. In view of this problem, a need exists for a process and associated apparatus to reduce leakage of the toner 8.